A well operating obd 2 fuel system from 96-2003 magnum v8's is approximately 40-52psi. You'll get about 6% more flow at this pressure from a given inj compared to operating at 43.5psi which inj's are rated at typically. That's why in 2000, they changed the rating to 21lb injectors. I guess they noticed they overlooked this factor because nothing changed really from '99 to 2000 except style of connector and some emmissions parts. Same fuel pressure.

If you want the best economy and performance, I would look into a ford 4 hole injector with the smaller body. The lighter components inside allow for better fuel control and if needed you can run them over 80% duty cycle because of the lighter internal components. I don't mess with obd 1 so I can't help there.